Data for: Coupled anaerobic methane oxidation and metal reduction in soil under elevated CO2

Continued current emissions of carbon dioxide (CO2) and methane (CH4) by human activities will increase global atmospheric CO2 and CH4 concentrations and surface temperature significantly. Fields of paddy rice, the most important form of anthropogenic wetlands, account for about 9% of anthropogenic sources of CH4. Elevated atmospheric CO2 may enhance CH4 production in rice paddies, potentially reinforcing the increase in atmospheric CH4. However, what is not known is whether and how elevated CO2 influences CH4 consumption under anoxic soil conditions in rice paddies, as the net emission of CH4 is a balance of methanogenesis and methanotrophy. In this study, we used a long-term free-air CO2 enrichment experiment to examine the impact of elevated CO2 on the transformation of CH4 in a paddy rice agroecosystem. We demonstrate that elevated CO2 substantially increased anaerobic oxidation of methane (AOM) coupled to manganese and/or iron oxides reduction in the calcareous paddy soil. We furth..., File 1 and File 5: We incubated the soils from the two paddy systems to examine whether anaerobic oxidation of methane could be coupled to the reduction of nitrate (NO3-), manganese (Mn(IV)), iron (Fe(III)) or sulfate (SO42-) in soils (exp. 1). Soil slurries were anaerobically incubated following a completely randomized design (CRD), in which two main factors were 13CH4 (no 13CH4 addition vs +13CH4) and e-acceptor (no e-acceptor addition, +NO3-, +Mn(IV), +Fe(III), and +SO42-). Each treatment replicated 3 times. We measured 13CH4 consumption, 13CO2 production and Mn2+/Fe2+ production after incubation.
File 2: We incubated the soils from the rice FACE system to investigate the influence of eCO2 on the coupling of anaerobic oxidation of methane to metal reduction. Soil slurries were incubated following a split-plot experiment with factorial structure, and whole-plots were organized as a RCBD (3 blocks). The CO2 treatment (aCO2 vs eCO2) was considered the whole-plot factor, while the two ne...,